Abstract

Optimizing photorefractive charge density for contradirectional two-beam coupling suggests doping photorefractive crystals with high impurity concentrations. A series of Rh-doped SBN:60 samples with Rh concentrations ranging from 0.015 to 0.20% by weight were grown and fabricated. The corresponding absorption coefficients α, extending from 0.5 to 6.2 cm⁻¹, are a penalty for such high doping levels. These α are non-negligible when compared to the measured contradirectional two-beam-coupling coefficients Γ, which ranged from 0.8 to 13.8 cm⁻¹. In this regime of non-negligible α, the simple analytic expressions derived by Yeh¹ are no longer valid. Ja² has provided an applicable theoretical description giving a numerical solution. We have extended Ja’s work, deriving an approximate expression for the two-beam-coupling gain g in the presence of strong α, which ranged from 0.8 to 13.8 cm⁻¹. In this regime of non-negligible α, the simple analytic exp which is a function of α, Γ, thickness L, and incident pump-probe intensity beam ratio r_pp. We will present g versus r_pp data for six different Rh concentrations and compare that data to various theoretical predictions.

© 1992 Optical Society of America